1. Field of the Invention
The present invention relates to a color image forming apparatus such as a printer or a Multi Function Peripheral (MFP), and in particular to the timing of an image stabilization operation.
2. Related Art
In a color image forming apparatus, optimum control variables for image formation are altered by changes in internal temperature and humidity and deterioration of parts such as photoreceptor drums and developer. For this reason, the image stabilization operation is performed under certain conditions to modify the control variables of apparatus parts in order to maintain a print image quality that is greater than or equal to a certain required reference image quality (required image quality).
Some issues that occur in this kind of image stabilization are that commodities (developer, etc.) are consumed, and a user is kept waiting during a downtime of the apparatus while the image stabilization operation is being performed. There is a conventional technology for optimizing conditions for performing image stabilization.
However, if a fixed condition is used as a condition for performing the image stabilization operation (e.g., when a printed sheet count reaches a certain sheet count), undesirable situations may occur, such as long downtime due to frequent premature image stabilization, or inferior printing continuing for a long duration due to late performance of image stabilization.
In the first place, image stabilization should be performed before the image quality falls below the required level. When determining the timing to perform image stabilization in a color image forming apparatus, particular consideration should be given to the fact that the required image quality is much more demanding in color printing than in monochrome printing.
The present invention has been achieved in view of the above issues, and an aim thereof is to provide a color image forming apparatus that can perform image stabilization at a timing appropriate for current conditions, taking into account the difference in required image quality between color and monochrome printing, user tolerance pertaining to downtime, etc.